A lot of research has demonstrated that the capacity of astaxanthin in cleaning free radicals is 10-fold that of β-carotene, and 100-fold that of vitamin E. It was also found that astaxanthin can penetrate the blood brain barrier (BBB) and directly provide an antioxidant effect on the central nervous system of the brain.
At the present time, astaxanthin is mainly chemically synthesized and is used as an animal feed, a nutritional supplement and a food pigment. Since the synthesized astaxanthin contains a specific enantiomer and its effect on human health is not totally understood, there is doubt about whether the synthesized astaxanthin is suitable as an additive in health foods. Therefore, astaxanthin from biological sources will be mainly used in future. Furthermore, in order to encourage the utilization of additives from their natural sources, many European countries and the United States of America are passing legislation to limit the use of chemically synthesized compounds as feed additives.
The known natural sources of astaxanthin are shrimps, crabs, fishes, feathers of birds, yeast, algae, etc. U.S. Pat. No. 3,906,112 discloses a method for extracting astaxanthin from shrimp processing waste which comprises the step of extracting with soybean oil at a temperature of 80-90° C. U.S. Pat. No. 4,505,936 discloses a process for extracting astaxanthin using the steps of removing proteinaceous tissue from the chitinous shell and then extracting astaxanthin from the chitinous shell with a vegetable oil. U.S. Pat. No. 5,210,186 discloses a process for recovering astaxanthin from shrimps and other crayfish by utilizing an alkaline solvent during boiling. CN 1824652 relates to a process for extracting astaxanthin from plants with the utilization of supercritical fluid CO2. U.S. Pat. Nos. 5,599,711, 5,356,810 and 5,972,642 pertain to the processes for extracting astaxanthin from Phaffia rhodozyma. Since astaxanthin produced by P. rhodozyma is presented in the cell plasma, in order to obtain astaxanthin from cells, they must be treated by a method that can break the cell wall or allow astaxanthin to pass through the cell wall. In such U.S. patents, the yeast cells must be dried and the drying process will increase the complexity of extraction, decrease the production of astaxanthin because of the loss of astaxanthin during the processing, and increase the consumption of energy. U.S. Pat. No. 4,871,551 discloses a method for obtaining astaxanthin from Heamatococcus pluvialis with the utilization of suitable organic solvents, e.g., oils, aromatics, halogenated hadrocarbons, and alkanes. WO 2007/029627 discloses a process for extracting astaxanthin from Heamatococcus pluvialis with the utilization of supercritical fluid CO2. U.S. Publication No. 2007/0196894 discloses a method for separating free-astaxanthin from Heamatococcus pluvialis, and the method comprises the steps of extracting with an alkanic solvent and then extracting with an alcohol.
Pomacea canaliculata (Lamarck) (Gastropoda, Ampullariidae), also named apple snail, has become a serious calamity in agriculture around the world because of its strong reproductive capacity and its ability to extend its geographical range. The eggs of the apple snail are spherical and pink to red. It has been found that its eggs and gonads contain a large amount of astaxanthin. The present invention found an effective method to extract and purify the natural astaxanthin from the eggs and gonads of the apple snail.